The present invention pertains to a control for an electrophotographic copying machine and, more particularly, to a method for controlling an electrophotographic copying machine by means of a single control element.
It is conventional in the art of an electrophotographic copying machine that a plurality of microswitches are provided for sensing events in the sequence of operation of the machine, the respective outputs of the microswitches being useful to determine the next succeeding events.
Briefly speaking, in the electrophotographic copying machine, there is provided a photo-sensitive member or a master paper carrying a photoconductive layer deposited on the upper surface of an electrically conductive layer. First, uniform charge is carried out on the photoconductive layer on the master paper. If the photoconductive layer is exposed to a light pattern, the corresponding electrostatic latent image is formed thereon. Thereafter, the latent image is developed in a visual form by means of toners through a development station. A copy sheet after being fed is forced into a close contact position with the photosensitive member to transfer the toner image onto the copy sheet which in turn is sent to a fixing station for the purpose of fixing the toner image. The copy sheet is finally sent to an outlet.
As briefly stated, the sequence of copying operation consists of the charging, light exposing, developing, transferring, fixing steps, etc., and these steps are under control of the microswitches which sense the feeding states of the copy sheet and the rotation position of the photosensitive drum.
In this case, a control circuit is essentially complicated and needs a number of wirings communicating with the microswitches. The control circuit is typically composed of cascade connected stages of TTL-IC's. Taking an example of the charging station, the control circuit provides charging control signals and operates the charging station via a driver circuit. However, the microswitches cannot be focused on a single position because of operational and physical problems.
Meanwhile, solenoids are employed as a means of transducing respective sensing outputs inclusive ones indicative of copy sheet jam into mechanical outputs. There is created a possibility that the whole of the machine inclusive of these solenoids serves as a source of noises for the electronic control circuits. It is obvious that the control circuits undergo the influences of the noise source because of complexity and extended length of wirings. In addition, while the essential steps of the machine such as the charging, the light exposure and movement of an original table are carried out in synchronization of the master paper, the control circuits operate in response to signals inputted in an asynchronous mode. Therefore, they are susceptible to noise.
The control for the electrophotographic copying machine needs a sufficiently long period of time to return of the original table upon operation of a print start switch. Nevertheless, it is not necessarily required to perform the sensing operations of the microswitches in a parallel fashion. If time permits, the operating states of the family of the switches can be confirmed in a serial fashion. Such conversion into the serial control permits extra wirings to be avoided and maximum allowance for noise to be enhanced.